1. Field of the Invention
The present invention relates to guidance of earthmoving machines and especially machines employed for laying drainage elements.
2. Description of the Prior Art
Machines of this type are used for the drainage of agricultural land by burying in the ground on the one hand a series of drains disposed in parallel relation to catch excess water in the ground and on the other hand mains or header pipes which are disposed transversely with respect to the drains and to which the latter are joined in order to convey drained water to an outfall. To this end, a machine of this type is provided with a coulter for forming a furrow in the ground as well as a system for laying drainage elements placed behind said coulter and subsequently buried in the ground. However, in order to permit the flow of collected water from the drains into the header pipes, these different drainage elements must be laid at a suitable angle of slope or gradient down to the outfall.
Under these conditions, any drainage site entails the need for a design study with a view to establishing a preliminary project for determining the planimetric location line of each drain or header with its altimetric profile. In the case of each drain section or header section, this project is defined by:
the planimetric coordinates of its origin and of its end; PA1 the height of its origin (or its depth with respect to the natural ground); PA1 the slope (gradient) and length of the segments constituting the longitudinal profile. PA1 one module for planimetric guidance of the corresponding machine; PA1 and the other module for altimetric guidance of the digging tool of this machine.
This project also mentions the planimetric coordinates of certain points which give rise to special operations such as, for example, a change in nature of the material employed (change in diameter of piping, use of a perforated or non-perforated pipe) or else the addition of a predetermined accessory such as, for example, an inspection hole and the like.
At the time of laying of drainage elements, it must be ensured that the laying machine is suitably guided over the ground in order to follow a series of paths corresponding to the intended locations of the different drainage elements and also that the level of its drain-laying tool in the ground is so adjusted as to conform to the profile which has been established for these drainage elements.
The method in use at the present time consists first in marking out on the ground by means of stakes and by conventional topographic methods all the characteristic points of the planimetric location line of the drainage project. It is then only necessary for the operator of the drain-laying machine to follow the alignment of corresponding stakes by sight in order to comply with the planimetric line.
In regard to compliance with the altimetric profile, this is obtained on the ground with respect to a reference plane which is inclined to the horizontal and is generated by a rotating laser beam emitter. To this end, the drain-laying tool comprises a receiver for detecting the passage of the laser beam. Under these conditions, the drain-laying machine operator must read the gradient of the drain section concerned on the project layout plan and consequently adapt the guidance gradient assigned by the laser beam emitter. After this preliminary adaptation, the equipment provided automatically maintains the drain-laying tool at the chosen angle of slope.
This method therefore calls for a large number of preliminary operations, thus producing a corresponding rise in capital costs for drainage work. The most time-consuming operations are clearly those which involve marking the planimetric line on the ground by placing a sufficient number of stakes.